Continuous disk winding and integral radial coil connector for electric transformer and the like



Sept. 16, 1969 J. c. DUTTON 3,467,931

CONTINUOUS DISK WINDING AND INTEGRAL RADIAL COIL CONNECTOR FOR ELECTRICTRANSFORMER AND THE LIKE Filed Sept. 23, 1966 2 Sheets-Sheet 1 FROMSTE/P SUPPL RL Sept. 16, 1969 J. c. DUTTON 3,467,931

CONTINUOUS DISK WINDING AND INTEGRAL RADIAL COIL CONNECTOR FOR ELECTRICTRANSFORMER AND THE LIKE Filed Sept. 23, 1966 2 Sheets-Sheet 2 l //vVE/V TOR. I

JoH/v C. urro/v In /p0 144M ATTORNEY United States Patent 3,467,931CONTINUOUS DISK WINDING AND INTEGRAL RADIAL COIL CONNECTOR FOR ELECTRICTRANSFORMER AND THE LIKE John C. Dutton, Rome, Ga., assignor to GeneralElectric Company, a corporation of New York Filed Sept. 23, 1966, Ser.No. 581,525 Int. Cl. H01f 27/30 US. Cl. 336-180 6 Claims ABSTRACT OF THEDISCLOSURE A transformer winding comprising a plurality of axiallyadjacent disk coils wound from one continuous band or strip of wide,thin electric conductor. Each coil is spirally upwound and radial crossconnectors between radially offset winding turns are formed integrallywith the coils by forming in the strip material a series of flatangularly disposed folds and intermediate perpendicular bends.

The present invention relates to inductive windings for electrictransformers and the like, and more particularly to windings formed ofone or more spirally wound disktype coils wherein radially offset turnsof the same or of adjacent coils are electrically connected incontiguous series circuit relation.

In inductors carrying heavy currents, special conductors must beemployed to prevent excess heating due to the passage of current throughthe conductors in the inductor windings. One type of high currentconductor commonly employed is of rectangular cross-section approachinga square, i.e., having a low width-to-thickness ratio of the order ofunity. This type of relatively thick conductor is used to formconcentrically Wound disk type coils, a number of which are usuallyfound on a common core or mandrel in axially spaced relation. Each diskcoil is formed from one or more strands of conductor material, and isspirally wound upon itself beginning at the surface of a suitable reelor mandrel, usually formed as a cylinder of insulating material. Theprocess of winding a 'disk coil from the reel radially outward is knownin the art as upwinding.

In prior art inductors, axially adjacent upwound coils have beenconnected in series by cutting the coil conductor at the inner and outerends of each coil and connecting a special crossover conductor from theoutermost turn of one coil to the innermost turn of an adjacent coil.Such special crossover conductors have previously been formed separatelyof relatively wide thin material, because the usual coil conductor oflow width-to-thickness ratio is too thick to use in the small spacebetween axially adjacent coils. These axial spaces between coils act asducts to conduct cooling fluid radially, so they must not be undulyobstructed. Also, if spacing between the coils and crossover is toosmall, insulation problems arise. Such separate crossover connections,however, must be brazed at each end, so that manufacture is costly andthe additional connections increase coil resistance and the possibilityof failure. 1

i It is one object of the present invention to obviate the need forseparate crossover conductors between radially offset turns of disk typecoils.

It is a more particular object of the present invention to provide aninductive winding having axially adjacent upwound coils with integralcrossover connectors extending between the outermost turn of one coiland the innermost turn of the next adjacent coil.

It is a still further object of the present invention to provide aninductor having integral coil crossover connectors which may befabricated during a continuous winding process.

It is still another object of the present invention to provide aninductive winding of the upwound disk type having integral coilcrossover connectors which occupy a minimum axial distance in the spacebetween adjacent coils.

In carrying out my invention in one preferred embodiment, I upwind aplurality of disk-type coils from a flat strip conductor having arelatively large width-tothickness ratio. This wide, thin coil conductoris itself utilized to form integral crossover connectors. By forming acombination of flat angular folds and intermediate perpendicular bends,a connecting section of the coil conductor is radially offset to providean integral cross connector between electrically contiguous turns of thesame or axially adjacent upwound coils.

By forming disk-type coils of strip material which is wide relative toits thickness, there is provided a large conductor cross section for anypredetermined conductor thickness. The resulting high current capacityof the coils requires an axial spacing (for cooling) which is largerelative to conductor thickness, so that the integral radially disposedcross connection does not unduly obstruct the inter-coil duct.

While this specification concludes with claims particularly pointing outand distinctly claiming my invention in its essential aspects, theobjects and advantages of the invention will be more fully understood byreferring now to the following detailed description taken in conjunctionwith the accompanying drawings in which:

FIGURE 1 is a perspective view of an inductive winding constructed inaccordance with the teachings of the present invention;

, FIGURE 2 is a plan view of a segment of a conductive strip having foldlines which allow the fabrication of an integral coil crossoverconnector in accordance with the teachings of the present invention;

FIGURE 3 is an enlarged perspective view of a coil connector fabricatedin accordance with the teachings of the present invention;

FIGURE 4 is a perspective view of one coil of an inductor showing meansfor holding the coil strands in position;

FIGURE 5 is a schematic diagram showing the use of the present inventionfor transposing the strands in a multistrand disk-type winding;

FIGURE 6 is an enlarged perspective view of a coil connector used fortransposing strands;

FIGURES 7 and 8 are diagrammatic illustrations of partially interlacedcoils using my invention, and

FIGURE 9 is a fragmentary perspective view of a re-entrant crossconnector for the interlaced coil of FIG. URE 8.

Referring now to FIGURE 1, there is shown an inductive winding disposedupon a tubular support or core member 10 of insulating material andcomprising a plurality of axially spaced coils 11-16 of the upwounddisktype. The winding is fabricated by winding the coils from relativelywide flat strip material, starting with coil 11 and finishing with coil16. The winding of coil 11 is begun at the radially inner end adjacentthe core member 10 after bringing out a terminal end or lead 17 shownextending parallel to the insulating core member. It will be evident tothose skilled in the art that the tubular core member 10 may in finalassembly be disposed on a rectilinear core of magnetizable material (notshown).

The coil conductor is a relatively wide, thin band of strip materialhaving a large width-to-thickness ratio as compared with rectangularconductorsnow commonly used to wind disk-type coils. Preferably the thinconductor strip or band is formed of extruded aluminum or copper havinga width of several inches and a thickness the order of 30 to 300 mils.For example, I have Wound a satisfactory experimental multicoil windingof conductor 75 mils thick and two inches wide. Such a band of stripmaterial must be suitably insulated, such as by a coating of insulatingenamel or paper.

After the terminal end 17 is secured to the insulating core member 10,the core member is rotated so that the strip conductor is continuouslywound on itself to radially build up, or upwind, the multi-turn coil 11.When the desired number of turns has been wound, a crossover connector18 is formed at the end of the outermost turn of coil 11. The coilcrossover connector 18, which is described in greater detail in thefollowing paragraphs, is shaped to bring the band of strip of materialto a new radially inset position on the surface of core member where itis parallel to and spaced axially from the turns of the coil 11. Theconductor band or strip at the new position forms the beginning of coil12. The winding process is then repeated until the desired number ofturns has been wound for coil 12. A coil crossover connector 19,identical to the connector 18, is formed at the end of coil 12 so as tobring the strip back to the core member surface. The above-describedwinding process is repeated for coils 13-16 with the crossover sections20, 21 and 22 being formed to provide electrical connections be tweencoils 13, 14, and 16. Upon completing the coil 16, the conductor stripmay be again folded as shown and brought out along the surface of coremember 10 to form a terminal lead 23.

An inductive winding such as that shown in FIGURE 1 may serve as thehigh or low voltage winding in a transformer. It is especially useful asa low voltage winding because of the high current-carrying capacitywhich can be provided in the wide, fiat conductor. To provide symmetryand balance in the winding, the cross connectors 18-22 are preferablystaggered around the periphery of the winding. Although FIGURE 1 showsthe coil connectors 18-22 offset about only part of the coil periphery,this is for purposes of illustration only. In a preferred embodiment ofthe invention, the coil connectors 18-22 would be distributed about thefull periphery of the winding.

FIGURE 2 shows a portion 24 of my coil conductor strip upon which isillustrated, by dotted lines, lines along which the material may befolded in order to form the coil crossover connector of the presentinvention. Starting at the left end of the coil strip 24, a first end 25would be at the end of the outermost turn of a completed coil. The end25 terminates at a fold line 26 which lies at an angle of 45 degrees tothe side edges 27 and 28 of the strip. A pair of parallel bending lines29 and 30, perpendicular to the edges 27 and 28, define an intermediateportion 31 which constitutes the radially offset part of the finishedconnector. At the right of the strip there is another 45 degree foldline 32 extending parallel to the fold line 26. The perpendicular bendline and the 45 degree fold line 32 define two of the edges of atrapezoidal portion 33 just as the perpendicular bend line 29 and the 45degree fold line 26 define a trapezoidal portion 34. The area of thestrip to the right of the fold line 32 is a second end 35 of the stripportion 24. When the segment 24 is folded, the end 35 constitutes thebeginning of the innermost turn of a new coil which is parallel to butaxially spaced from the completed coil. The axial spacing or offset ofthe coils is determined by the sum of the distance A (measured along thestrip from the perpendicular fold line 29 to the nearest end of thedegree fold line 26) and the distance B (measured along the strip fromthe perpendicular fold line 30 to the nearest end of the 45 degree foldline 32).

The blank shown in FIGURE 2 is shaped into the desired coil connectorshown in FIGURE 3 in the following manner. Once the outermost turn ofthe completed coil with the end 25 is secured to the subjacent turn ofthe coil, the strip is folded upon itself along the 45 degree line 26until the trapezoidal portion 34 overlies part of the end 25. Ahydraulic or hand press may be used to flatten the trapezoidal portion34 against the end 25. The bending continues in the same direction atthe perpendicular fold line 29 until the intermediate radial offsetportion 31 is at right angles to the end 25 that extends radiallyinwardly. This bend causes the intermediate portion 31 to extend alongthe side edges of the completed coil turns. Thestrip is then bentdegrees in the opposite directions at the perpendicular fold line 30, sothat the trapezoidal portion 33 rests on the reel surfaces with its sideedges at right angles to the side edges of the strips in the completedcoil. To complete the coil connector, the strip is folded upon itselfalong the 45 degree fold line 32 so that the end 35 extends in the samedirection as the end 25 of the completed coil. The axial distance, orthe distance along the reel surface, between the adjacent coils isdetermined by the sum of the distances A and B as is shown in FIGURE 3.When the new coil has been completely wound, this bending process isrepeated, bringing the strip from the outer layer of the newly completedcoil back to the reel surface.

The end 25 of the outermost coil turn may be secured to the subjacentturn by taping or cementing it. Alterriatively, the arrangement shown inFIGURE 4 may be utilized. A coil 36 shown there is wound on a reel 42between the arms of U-shaped spacers 37 having their bight portionsresting against the reel surface. The U- shaped spacers serve as guidesduring the winding process of lining up the side edges of the coilturns.. To secure the outermost turn of the coil, there are providedadditional U-shaped spacers 38 which are inverted relative to thespacers 37. That is, the bight portion of each of the inverted spacers38 rests on the outermost turn of the coil and its arms extend inwardlyalong the sides of the coil to the reel surface. The inverted spacers 38may be secured to the reel surface by any suitable means.

The above-described coil connector may also be used to transpose strandsin a multi-strand conductor strip. Such multi-strand strips are used inwindings which are to carry extremely heavy currents. By usingrelatively thin strands to make up each strip, the desiredcrosssectional area of the conductor may be obtained without incurringthe eddy current losses which would occur in a single strand striphaving the same cross-sectional area. The relative positions of thestrands in each strip should be altered so that each strand links thesame amount of flux. This equal flux linkage produces the same voltagein each strand so that there are no circulating currents betweenstrands.

FIGURE 5 shows diagrammatically a transposition arrangement for aWinding made from a three-strand strip. For purposes of simplicity, eachcoil is shown as having only three multistrand turns, each of which ismade up of bands or strips A, B, and C. In the left-hand group 39 of thecoils, the strands are in the same position relative to one another,i.e., strand A is at the top of each turn, whereas strand C is at thebottom so that the strip has an ABC configuration. In the adjacent ormiddle group 40, however, strand A is moved from the top to the bottomof each coil turn, whereas strand B occupies the top position and strandC the intermediate position to form a turn having an BCA configuration.This transposition is brought about by altering the connection patternbetween the right-hand coil in group 39 and the left-hand coil in group40.

FIGURE 6 is a perspective view of a strand-transposing cross connectionof the type illustrated at FIGURE 5 between the coil groups 39 and 40.The cross connector for the strand A is formed first to bring strand Afrom the outside of the top turn of the completed coil down against thereel surface. Then the connector for the innermost strand C is formed.Strand B, the intermediate strand in the completed coil, is extendedpast the connector for the strand C before its own connector is formed.In the new coil, strand B is at the outside whereas strand A is at theinside of each coil turn. Each of the coils in group 40 of FIGURE 5 iswound with this arrangement of strands. The strands ABC may .-,besimilarly transposed between the right-hand coil in the group 40 and thelefthand coil in group 41 of FIGURE 5.

Although FIGURE 5 shows three coil groups 39, 40 and 41 having threeidentical coils each, it is not necessary to group the coils in anyparticular way so long as each strand occupies the same position thesame number of tirn'esas each of the other strands. For example, thefirst coil in a group of three coils c ould be provided with an ABCstrand configuration, the second coil with a BCA configuration, and thethird with a CAB configuration.

It will now be evident to those skilled in the art that my improved coilconductor and integral flat crossover connector may be utilized not onlyto interconnect entire coils, but may be used also to provide theinternal cross connections characteristic of so-called interlaced coils.Coil interlacing of one type is described, for example, in Patent2,453,552-Stearns, and is illustrated diagrammatically at FIGURE 7forming, part of my present specification. At FIGURE 7, I have shownthree upwound coils with the first two coils at the left side interlacedand the third coil directly stacked, the coil turns being connectedelectrically in series in the order indicated by the numbers on theturns. ,It will be evident that the coil cross connectors shown may allbe formed in the manner previously described.

In addition, it is known to interlace disk coils in a manner such thatat least some of the internal cross connectors are re-entrant into thesame coil, as illustrated in the single interlaced coil showndiagrammatically at FIGURE 8. In that figure the intercoil crossconnector 50 may be formed as previously described, while the reentrantcross connector 51 is formed without axial offset, such as illustratedin perspective at FIGURE 9. The reentrant strip of FIGURE 9 is formed byfolding along 45 degree and 90 degree lines in somewhat the manner shownat FIGURE 2, but with the 45 degree end folds made along mutuallyperpendicular, rather than parallel, 45 degree lines.

While there has been described what I now consider to be a preferredembodiment of the persent invention, it is apparent that modificationsand variations may occur to those skilled in the .art. Therefore, it isintended that the appended claims shall cover all such modifications andvariations as fall within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. In an inductive winding for electric transformers or the like, alinear core member, at least two spirally wound disk coilsconcentrically mounted on said core in axial spaced relation, each saidcoil comprising a plurality of radially superposed turns formed of athin band of wide electrically conductive strip material, and anintegral crossover connector extending substantially radially along theedges of said turns between said coils to connect in continuous seriescircuit relation a pair of radially offset turns of said winding, saidconnector being formed by folding said band of strip material uponitself at two spaced-apart points along fold lines acutely angularlydisposed with respect to the axis of said band and bending the bandsubstantially at right angles at two intermediate points along linessubstantially perpendicular to said axis.

2. A Winding according to claim 1 wherein said radially offset turns arein a single disk coil and said acutely angularly disposed fold lines aremutually perpendicular and said band of strip material is bent in thesame direction at said intermediate points, whereby said crossoverconnector is re-entrant in respect to said single coil.

3. A winding according to claim 1 wherein said radially offset turns arein adjacent axially offset coils and said acutely angularly displacedfold lines are mutually parallel so that said crossover connectorextends axially between said coils and radially between said turns.

4. A Winding according to claim 1 including at least two axiallyadjacent upwound coils and wherein said crossover connector extends fromthe outermost turn of one coil to the innermost turn of the other.

5. A winding according to claim 1 including at least two axiallyadjacent upwound coils and wherein said angularly disposed fold linesare mutually parallel and at substantially 45 degrees to the axis ofsaid band of strip material, said band being bent in opposite directionsat said intermediate points, whereby said crossover connector extendsaxially of said winding between said coils and radially between saidturns.

6. An inductive winding according to claim 1 wherein said radiallyolfset turns are in adjacent axially offset coils and each is formed ofa plurality of superposed bands of strip material, each said band beingfolded and bent to form a separate crossover connector and saidconnectors being positioned to transpose the relative positions of saidbands in passing between said coils.

References Cited UNITED STATES PATENTS 3,008,107 11/1961 Stearn 3363,188,591 6/1965 Dortort et al. 336 3,371,300 2/1968 Stein 336187 XFOREIGN PATENTS 22,313 8/1930 Netherlands. 256,158 12/ 1927 Italy.

WARREN E. RAY, Primary Examiner US. Cl. X.R. 336-187, 232

